Visual Studio is actually quite fast if used properly. For example, I have solution with 45 projects (~600000 loc) that works fine.

It's probably an installed extension that kills the IDE (things like Resharper for example can be memory greedy - disclaimer: I have nothing against Resharper, I use it myself :-).

Here is a link to disable extensions (read also the comments): How to: Disable and Re-enable Visual Studio Tools and Extensions